Long Range Surface Plasmons assisted highly sensitive and room temperature operated NO2 gas sensor

Abstract

Long Range Surface Plasmons (LRSPs) are excited in the SnO2/Au/SnO2/prism structure using Kretschmann configuration for detecting NO2 gas. SnO2 thin films of two different thicknesses are grown by RF sputtering technique and 205 nm thin SnO2 film resulted in the sharp LRSP resonance (LRSPR) reflectance curve with the minimum reflectance (Rmin) = 0.05 at the resonance angle (θspr) of 42.38°. LRSPR based room temperature (22 °C) operated gas sensor using the optimized SnO2/Au/SnO2/prism configuration is developed in the present work for effectively detecting NO2 gas in a broad concentration range from 0.5 ppm to 2000 ppm. The LRSPR reflectance curve corresponding to the prepared sensor shows an appreciable shift of 8.47° in the resonance angle on exposure to NO2 gas (2000 ppm). The developed optical sensor illustrated high sensitivity (0.2°/ppm) along with the limit of detection (LOD) of 0.38 ppm of NO2 gas. The sensor exhibited outstanding selectivity towards NO2 gas and showed insignificant response to various other interfering gases. The obtained results highlight the successful fabrication of competent LRSPR based optical gas sensor capable of detecting NO2 gas at room temperature.